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/* Copyright 2019 David Grote, Maxence Thevenet, Remi Lehe
* Weiqun Zhang
*
* This file is part of WarpX.
*
* License: BSD-3-Clause-LBNL
*/
#ifndef WARPX_PARTICLES_PUSHER_UPDATEPOSITION_H_
#define WARPX_PARTICLES_PUSHER_UPDATEPOSITION_H_
#include "Utils/WarpXConst.H"
#include <AMReX_REAL.H>
#include <AMReX_FArrayBox.H>
/** \brief Push the particle's positions over one timestep,
* given the value of its momenta `ux`, `uy`, `uz` */
AMREX_GPU_HOST_DEVICE AMREX_INLINE
void UpdatePosition(amrex::ParticleReal& x, amrex::ParticleReal& y, amrex::ParticleReal& z,
const amrex::ParticleReal ux, const amrex::ParticleReal uy, const amrex::ParticleReal uz,
const amrex::Real dt )
{
using namespace amrex::literals;
constexpr amrex::Real inv_c2 = 1._rt/(PhysConst::c*PhysConst::c);
// Compute inverse Lorentz factor
const amrex::Real inv_gamma = 1._rt/std::sqrt(1._rt + (ux*ux + uy*uy + uz*uz)*inv_c2);
// Update positions over one time step
x += ux * inv_gamma * dt;
#if (AMREX_SPACEDIM == 3) || (defined WARPX_DIM_RZ) // RZ pushes particles in 3D
y += uy * inv_gamma * dt;
#endif
z += uz * inv_gamma * dt;
}
#endif // WARPX_PARTICLES_PUSHER_UPDATEPOSITION_H_
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